1. Field of the Invention
The present invention relates to a prefabricated formwork for concrete and more particularly to a collapsible prefabricated formwork for concrete walls.
2. Description of Prior Art
The time-tested method of constructing concrete walls for buildings include the pouring of concrete into a formwork set up, in situ. This operation includes the erection of the formwork which includes a pair of vertical sheathing panels in a spaced relationship by means of connecting elements. Such formwork is either of the removable and thus reusable type or is of a lost form type wherein the formwork becomes part of the structure after the concrete is cured. A lost form of formwork utilizing sheathing panels of insulating material is called generally an insulating formwork.
All known insulating formwork comprise a connecting element which connects the two sheathing panels. This type of formwork can be devided into two main categories depending on the arrangement between the connecting elements and the sheathing panels.
The first category may be referred to as a hollow parallelepiped blocks. In this category, one can find a connecting element which is molded with the sheathing at the factory site and is sometimes referred to by the trademarks ARGISOL and MARENGO. The advantages of this first category is that it is not necessary to install the connecting elements at the building site since they are already molded at the plant or factory with the two sheathing panels. On the other hand, this type of formwork has serious disadvantages in terms of storage or transportation given the rather high volume/surface-of-formwork ratio.
The second category is referred to as the planar solid slab formwork. In this category the connecting elements are normally rigid and are supplied separately from the sheathing panels which are in the form of the planar solid slabs. Examples of this category is shown in U.S. Pat. Nos. 4,604,843 and 4,888,931 and Canadian Patent 1,233,042. The disadvantages of this category of formwork is that the connecting elements must be assembled at the building site which increases the installation cost of the formwork.
The formwork of both of these categories is subject to other disadvantages at the on-site installation, and that is the relative small dimensions of the modules. For example in order to erect a 10 m.sup.2 formwork one must assemble 10 to 40 modules on site, depending on the type of formwork used, which increases the number of joints and the cost of installation. As far as the fabrication of these modules is concerned, various elaborate machining or molding procedures are required in order that the edges of the modules form proper joints on assembly.
Attempts to overcome these disadvantages have been made wherein the smaller modules are assembled at the factory site to form larger formwork sections and transporting these to the building site. In such a case one encounters transportation problems in view of the high volume to formwork surface ratio. That is a large volume of forms must be carried for a relatively small formwork surface. Each of the forms are of course spaced apart and held there by the rigid ties such that one lands up transporting a great deal of air.
On the other hand, once insulating formwork is being utilized, other tasks must be added such as the installation of reinforcement rods, vapor barrier, water proofing membranes, or filler strips. These additional tasks increase the installation costs and construction delays.
3. Summary of the Invention
It is an aim of the present invention to provide formwork which can be rapidly installed and which takes the advantages of the above mentioned two categories of insulating formworks without the disadvantages.
It is a further aim of the present invention to provide a prefabricated collapsible formwork which will reduce the amount of space required for storage or transportation as compared with the above prefabricated formwork.
It is further aim of the present invention to provide a prefabricated formwork which includes vapor barriers, waterproof membranes, insulation, reinforcement and filler strips already included at the factory site, thereby reducing the installation costs and construction delays at the building site.
It is a further aim of the present invention to provide prefabricated formwork modules which are of a greater size than those considered in the above two categories.
It is a further aim of the present invention to provide a prefabricated or preassembled collapsible formwork which one assembles at the building site and readies to receive concrete as well as the outside finish covering and the interior finish covering.
The construction in accordance with the present invention comprises a formwork for a vertical wall including a prefabricated formwork module for a vertical wall including a first sheathing panel, a second sheathing panel and a plurality of collapsible connecting elements anchored to each of the first and second sheathing panels and extending at least partially therebetween in a spaced apart relationship, the first and second sheathing panels including edges having joint means on edge areas for permitting the modules to be erected one to the other in edge to edge relationship, the formwork module and connecting elements being constructed such that during storage or transportation of the formwork modules, each formwork module is collapsed such that the first and second sheathing panel are adjacent one another with the connecting element collapsed and at the building site during assembly the first and second sheathing panels are spaced apart to the full extent of the connecting elements.
A method in accordance with the present invention comprises the steps of selecting a first sheathing panel having edges, selecting a second sheathing panel with edges to form a formwork module, attaching the first ends of a plurality of collapsible connecting elements to the first sheathing panel in a spaced apart relationship such that the connecting elements have opposite ends extending from the interior face of the first panel, connecting the opposite ends of the collapsible connecting elements to the second sheathing panel such that the interior face of the second panel faces the interior face of the first panel and collapsing the first and second sheathing panels against each other for storage and transportation while separating the first and second panels to the full extent of the connecting elements during assembly thereof at a building site. More particularly the method includes assembling a plurality of formwork modules, including providing joint means at the edge areas of contiguous sheathing panels of adjacent formwork modules.
In a more specific embodiment of the present invention there are provided bearing devices on the exterior of the first and second sheathing panels respectively and the connecting elements pass through the panels and abut the bearing devices. In a still more specific construction, the bearing devices are in the form of a filler strip and the sheathing panels are insulating panels. In a further specific embodiment, a concrete reinforcement in he form of a grid is assembled between the first and second sheathing panels at the factory site. Further, the vapor barrier and the waterproof membrane can be installed on the insulating sheathing panels at the factory site such that all of the component parts of the formwork can be preassembled at the factory site and the form can be collapsed for storage and transportation.
The erection of the formwork at the building site consists of separating the first ad second sheathing panels and by maintaining the separation by inserting spacers therebetween and connecting the joints at the edge areas of the panels with adjacent panels. In a more specific embodiment the spacers could be collapsible spacers which are preassembled at the factory site and which can be deployed at the building site when separating the first and second sheathing panels.
The invention is especially concerned with the preassembling of as many building components as possible on the formwork, at the factory site, and to use as much as possible, conventional building materials in order to avoid the necessity of molding processes such as for molding expandable polystyrene. It is an aim therefore to render the form construction as universal as possible.
Certain advantages which can be noted from the present invention include:
Reduced storage and transportation costs since the formwork utilizes collapsible connecting elements allowing the formwork to be collapsed, thereby reducing their respective volume to formwork surface ratio; PA1 A rapid and simple assembly of the prefabricated panels, and in particular a larger size module when using insulating sheathing panels, thereby reducing the number of assembling steps on the building site and the number of joints for a given formwork surface. For example to erect 10 m.sup.2 of formwork only three modules are required under the present invention instead of the current 10 to 40 modules.
The prefabrication of the sheathing panels is simple since no molding or machining of the panels is required. All that is required is to form holes through the sheathing panels.
A new form mating joint is described which offers resistance to traction and compression and this in two or three perpendicular directions. The system allows for rapid assembling and in case of errors an equally rapid disassembling of the modules.
Preassembling the vapor barriers, the waterproof membrane and the filler strips, both interior and exterior, as well as the concrete reinforcement at the factory site, eliminates having to provide for these steps at the building site, thereby reducing costs